*{
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}
#chapter{
  .focus_img{
    width:100%;
    height: 150px;
    overflow: hidden;
    background: url("/images/pc/study.jpg") no-repeat;
    background-size: 100%;
    background-position-y: -150px;
  }
  .menu{
    position: absolute;
    left: 0;
    width: 888px;
    padding: 20px;
    margin-top: 5px;
    background-color: #fff;
    .fold{
      width: 100%;
      padding: 20px;
      padding-bottom: 0;
      .chapter-item{
        position: relative;
        width: 100%;
        height: 64px;
        border-bottom: 1px solid #ccc;
        font-size: 20px;
        h4{
          position: absolute;
          left: 50px;
          top: 25px;
        }
        b{
          transition: .3s all ease-in-out;
          position: absolute;
          right: 50px;
          top: 20px;
        }
        }
    }
    .sections{
      width: 100%;
      display: none;
      padding: 0 40px;
      background-color: #fff;
      .section-item{
        width: 787px;
        height: 67px;
        padding-left: 40px;
        padding-top: 28px;
        color: #7e7e7e;
        border-bottom: 1px solid #ccc;
      }
    }
  }
}
#book_li {
  border-bottom: 2px solid #0084ff;
}
